Finally, having established a rough framework of relative values between skills and edges, and from noted a cost for their acquisition/improvement, we can turn to improving Attributes.
Let’s work with the idea that Edges and Characteristics have similar value. But they also have some differences: Edges have conditional rank requirements and any number of prerequisites; Characteristics have one limitative restriction insofar as they may only be improved ONCE per rank. This tells us that Characteristics should improve MORE slowly than Edges are gained or skills acquired/improved.
If we look to the costs for Edge acquisition as a baseline, we can increase point values accordingly to slow progression. Since Attributes and Edges will be paid for from the same pool of experience (General XP), we can adjust the apparent value to make Edges generally the more appealing purchase. The trick is not to make Attributes prohibitively expensive. And yet, there is also the issue of trying to keep costs relatively standard.
In this case, the law of FFF wins the day. Though attributes probably should cost a little more, it’s not worth having yet another cost progression to track. So Characteristics improve with the same cost increments as Edges, and calculated the same way as skills.
Characteristic Improvement XP Cost = (Next Die Type) x 10
Improving from d4 to d6 Costs 60 XP
Improving from d6 to d8 Costs 80 XP
Improving from d8 to d10 Costs 100 XP
Improving from d10 to d12 Costs 120 XP
And now we have a basic set of values. What remains to do is note how experience is given by the Game Master, and make any minor tweaks to the system before it is set down in its final form.